Production of o-aminobenzonitriles

ABSTRACT

Production of o-aminobenzonitriles by thermal decomposition of isatin Beta -oximes in the presence of basic compounds. The new products are starting materials for the production of dyes and pesticides.

United States Patent Goerth et al. 1 May 23, 1972 54] PRODUCTION OF 0-[56] References Cited AMIN BENZ NITRILES 0 0 UNITED STATES PATENTS [72]Inventors: Helmut Goerth, Ludwigshafen; Herbert Armbrust, Gruenstadt,both of Germany 3,374,262 3/1968 Seefelder et a1. ..260/465 73 Assignee:Badische Anilin & Soda-Fabrik Aktien- OTHER PUBLICATIONS gesellschflft,Ludwigshafen/Rhine, Bedford et a]. 5. Chem. Soc. (London) pp. 1633 1634many (1959). 22 F1 d: 23, 1969 1 June Primary Examiner.loseph Rebold[21] Appl.No.: 835,744 Assistant Examiner-D0lph H. TorranceAttorney-Johnston, Root, O'Keeffe, Keil, Thompson & Shur- [30] ForeignApplication Priority Data tlefi June 29, 1968 Germany ..P 17 68 786.4ABSTRACT Production of o-aminobenzonitriles by thermal decomposition[52] US. Cl ..260/465 E, 260/141, 260/310, of isafin 'B 0XimeS in thepresence of basic compounds The 260/325 260/999 new products arestarting materials for the production of dyes 51 1111. C1 ..C07c 121/78and pesticides [58] Field of Search ..260/465 E 8 Claims, No DrawingsPRODUCTION OF O-AMINOBENZONITRILES The invention relates to a processfor the production of oaminobenzonitriles by thermal decomposition ofisatin B-oximes in the presence of basic compounds.

It is known from the J. Chem. Soc. (London) 1633 et seq. (1959) thato-aminobenzonitriles can be prepared by decomposition of isatin B-oximesat from 200 to 300 C. At these high temperatures the reaction can onlybe controlled with difficulty if at all, only small amounts of startingmaterial can be reacted at a time, the yields are unsatisfactory and theprocess cannot be carried out economically on an industrial scale. Ithas therefore been proposed in US. Pat. specification N 0. 3,374,262that isatin B-oxime should be heated under subatmospheric pressure andin the presence of inert solvents or diluents so that theo-aminobenzonitrile formed immediately distils off. This method can becarried out with better yields on a large scale but it hasdisadvantages. It requires special apparatus, and reaction temperaturesof from 200 to 400 C. are given. In addition considerable amounts ofsolvent or diluent are necessary in this method. The carbon dioxideformed in the reaction disturbs considerably the setting up of thesubatmospheric pressure necessary for the distillation and considerableamounts of the o-aminobenzonitrile formed may be entrained, which oftenresults in stoppages in the apparatus and disturbances in operation.Avoiding these difficulties (pressure regulation, installation ofseparators, cleaning of the plant) makes the process more expensive.

it is an object of this invention to provide a new process for theproduction of o-aminobenzonitriles which is easier and more economicalto carry out and gives good yields of high purity product.

This and other objects are achieved and oaminobenzonitriles having thegeneral formula:

where the radicals R and R may be identical or different and eachdenotes a hydrogen atom, a halogen atom or an aliphatic radical areobtained advantageously by thermal decomposition of isatin ,B-oximes bydecomposing an isatin B-oxime having the general formula:

where R and R have the meanings given above, in the presence of a basiccompound at a temperature of more than 130 C.

As compared with prior art methods, the process according to thisinvention gives o-aminobenzonitriles in good yields and high purity by asimpler and more economical method. The process may be carried outwithout disturbance in standard apparatus, for example stirred vessels,at considerably lower temperatures and without solvent or with smalleramounts of solvent. Production of subatmospheric pressure required fordistillation is much simpler and special separators are not required.

Preferred starting materials are isatin B-oximes having the generalformula (II) where the radicals R and R may be identical or differentand each denotes a hydrogen atom, a chlorine atom, a bromine atom or analkyl radical having from one to four carbon atoms. For example isatinB-oxime itself and the following derivatives are suitable:S-methylisatin ,B-oxime, S-isobutylisatin ,B-oxime, S-chloroisatinfl-oxime, 5,7- dibromoisatin ,B-oxime and 4-methyl-5-chloro-isatinB-oxime.

Thermal decomposition of the starting material is carried out in thepresence of a basic compound. Preferred basic compounds are alkali metalcompounds or alkaline earth metal compounds or mixtures of the same, forexample hydroxides, oxides, amides; salts of weak or polybasic inorganicor organic acids such as acetates, propionates, carbonates,bicarbonates; alcoholates, glycolates, ether glycolates such asmethylates, ethylates, ethylene glycolates, nonaethylene glycolates,tripropylene glycolates, diethylenemono glycolate monomethyl ether andother alkylene glycolates (which may be etherified on one hydroxygroup), particularly ethylene glycolates and propylene glycolates.Sodium, potassium, calcium, barium and magnesium are preferred ascations for the said compounds. As a rule the basic compound or mixtureof basic compounds is used in an amount of from 0.01 to 10 percentpreferably from 0.05 to 5 percent, by weight with reference to startingmaterial (ll).

The reaction is carried out at a temperature of more than C., generallyat from 130 to 200 C. and preferably at from to C., at atmospheric orsuperatmospheric pressure, continuously or batchwise. It is advantageousto use organic solvents which are inert under the reaction conditions.Since the o-aminobenzonitriles often can be separated most favorablyfrom the reaction mixture by distillation, it is especially suitable touse solvents whose boiling point is sufficiently different from theo-aminobenzonitrile in question. The solvent preferably has a boilingpoint which is higher than that of the o-aminobenzonitrile preparedtherein, for example above 260 C. at standard pressure. Often only asmall amount of solvent is necessary because as the reaction proceedsthe oaminobenzonitrile formed serves as a solvent. Examples of suitablesolvents are hydrocarbons such as paraffin oil, petroleum fractions ofhigh boiling point, monoethylene glycols, polyethylene glycols,preferably based on ethylene oxide or propylene oxide, having a boilingpoint of more than 300 C. and a molecular weight of less than 1000 suchas hexaethylene glycol, nonaethylene glycol; monoethylene orpolyethylene glycol dialkyl ethers such as hexaethylene or nonaethyleneglycol dimethyl ether, dipropyl ether, diethylhexyl ether or mixturesthereof.

The reaction may be carried out as follows:

a mixture of starting material (ll) and a basic compound, with orwithout a solvent, is heated to reaction temperature while mixing welland the mixture is kept at'this temperature for some time. It isadvantageous to place only a portion of the starting material in thereactor and then to introduce the remainder into the mixture at thereaction temperature at such a rate that the temperature of the reactionchamber is kept constant, if necessary with additional cooling orheating. The commencement of the reaction is evidenced by thedisengagement of carbon dioxide. When carbon dioxide is no longerevolved, the end product is advantageously removed from the reactor bydistillation.

The temperature at which elimination of carbon dioxide takes place at anadequate rate is generally from 50 to 100 C. lower than the temperatureused in processes carried out without basic compounds as catalysts.

It is also possible to carry out the process continuously by feedingsolvent, catalyst and isatin B-oxime into a decomposition vessel kept atthe reaction temperature, continuously withdrawing a portion of thereaction mixture and supplying it to a distillation unit while isatin,B-oxime, catalyst and if necessary solvent are continuously fed in.

The compounds which can be prepared by the process are valuable startingmaterials for the production of dyes and pesticides. For example thecorresponding diazo compound can be prepared from o-aminobenzonitrile,this may be reacted with tin chloride to form the 3-aminoindazole (J.Am. Chem. Soc., 65, 1804 (1943)) and from this, by the process accordingto British Patent Specification No. 1,791,932, a dye salt may beprepared which is soluble in water and which will dye cotton mordantedwith tannic acid.

The invention is illustrated by the following Examples.

The parts given in the Examples are parts by weight.

EXAMPLE 1 Fifty parts of nonaethylene glycol, 0.5 part of sodiummethylate and 10 parts of isatin B-oxime are heated to 150 to 160 C.while stirring. After evolution of carbon dioxide has begun, another 690parts of isatin B-oxime is introduced at from 140 to 150 C. with ametering extruder. When the evolution of carbon dioxide has ceased, theoaminobenzonitrile formed is distilled off from the reaction mixture.443.4 parts (equivalent to 87 percent of the theory) of pureo-aminobenzonitrile is obtained having a boiling point (at 14 mm) offrom 135 to 139 C. and a freezing point of from 48 to 50 C.

EXAMPLE 2 0.2 part of sodium is dissolved in 60 parts of nonaethyleneglycol at from 80 to 90 C. Then 10 parts of isatin ,B-oxime is added andthe whole is heated to 150 to 160 C. so that elimination of carbondioxide begins. Another 315 parts of isatin B-oxime is then introducedat the same temperature into the mixture and stirred for another 10minutes. Distillation of the reaction mixture gives 205 parts (86.5percent of the theory) of 98 percent 2-aminobenzonitrile.

EXAMPLE 3 A mixture of 20 parts of S-methylisatin ,B-oxime, 3 parts ofanhydrous potassium carbonate and 250 parts of nonaethylene glycol isheated to about 165 C. while stirring. After evolution of carbon dioxidehas begun, another 510 parts of S-methylisatin B-oxime is slowlyintroduced while the temperature is kept at from 160 to 170 C. Evolutionof carbon dioxide ceases about 10 minutes after the addition iscompleted and then the reaction mixture is distilled. 316 parts (76.5percent of the theory) of 96 percent -methyl-2- aminobenzonitrile isobtained having a boiling point (at 1 mm) of from 1 15 to 1 18 C. and afreezing point of from 58 to 60 C.

EXAM PLE 4 Three hundred parts of nonaethylene glycol, parts of 5-chloroisatin B-oxime and parts of sodium acetate (anhydrous) are heatedto 165 to 170 C. while stirring. Reaction begins at this temperature andis evidenced by the evolution of carbon dioxide. During 50 minutes atfrom 160 to 170 C. another 190 parts of 5-chloroisatin B-oxime isintroduced. The mixture is then stirred for another 10 minutes at from160 to 170 C. and then distilled at a pressure of from 1 to 2 mm. Thedistillate which is kept liquid in a heated receiver is stirred intofrom 400 to 500 parts of water, allowed to cool, filtered and dried. 115 parts (74 percent of the theory) of pure 2amino5- chlorobenzonitrileis obtained having a freezing point of from 96 to 97 C.

EXAMPLE 5 Ninety parts of S-methylisatin B-oxime is decomposed in 30parts of paraffin oil in the presence of 0.6 part of sodium methylateduring 30 minutes at from 175 to 180 C. The distillation which followsgives 52.5 parts (73 percent of the theory) of 94 percent5-methyl-2-aminobenzonitrile.

We claim:

1. A process for the production of o-aminobenzonitriles having theformula.

NHz

where R and R may be identical or different and each denotes a hydrogenatom, a chlorine atom, a bromine atom or an alkyl radical having one tofour carbon atoms wherein an isatin B-oxime having the formula:

where R and R have the above meanings is decomposed in admixture with analkali metal or alkaline earth metal basic catalyst at a temperature ofC. to 200 C.

2. A process as claimed in claim 1 carried out in the presence of basiccatalyst in an amount of from 0.01 to 10 percent by weight withreference to the starting material ([1).

3. A process as claimed in claim 1 carried out in the presence of saidbasic catalyst in an amount of from 0.05 to 5 percent by weight withreference to the starting material ([1).

4. A process as claimed in claim 1 carried out at a temperature offromto C.

5. A process as claimed in claim 1 carried out in the presence of aninert organic solvent having a boiling point above 260 C. at standardpressure.

6. A process as claimed in claim 5 wherein said solvent is a hydrocarbonhaving said boiling point, a monoethylene glycol, a polyethylene glycolbased on ethylene oxide or propylene oxide and having a boiling point ofmore than 300 C. and a molecular weight of less than 1,000 or a dialkylether of said polyethylene glycol.

7. A process as claimed in claim 1 carried out in the presence of aninert organic solvent based on ethylene oxide or propylene oxide andhaving a boiling point of more than 300 C. and a molecular weight ofless than 1000.

8. A process as claimed in claim 1 wherein said basic compound is ahydroxide, oxide, amide, acetate, propionate, carbonate, bicarbonate,alcoholate, alkylene glycolate or monoether thereof with a sodium,potassium, calcium, barium or magnesium cation.

UNITED STATES PATENT OFFIfiE CERTIFIQATE QF CORRECTEUN Patent No. 5,665, O29 Dated Mav 25, 1972 Inventor(s) Helmut Goerth and HerbertArmbrust It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

First page, right-hand column, in the references, under "OTHERPUBLICATIONS", "S. Chem. Soc. should read J. Chem. Soc.

Column 2, line 71, "1,791,932" should read 791,952

Signed and sealed this 5th day of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents

2. A process as claimed in claim 1 carried out in the presence of basiccatalyst in an amount of from 0.01 to 10 percent by weight withreference to the starting material (II).
 3. A process as claimed inclaim 1 carried out in the presence of said basic catalyst in an amountof from 0.05 to 5 percent by weight with reference to the startingmaterial (II).
 4. A process as claimed in claim 1 carried out at atemperature of from 140* to 170* C.
 5. A process as claimed in claim 1carried out in the presence of an inert organic solvent having a boilingpoint above 260* C. at standard pressure.
 6. A process as claimed inclaim 5 wherein said solvent is a hydrocarbon having said boiling point,a monoethylene glycol, a polyethylene glycol based on ethylene oxide orpropylene oxide and having a boiling point of more than 300* C. and amolecular weight of less than 1,000 or a dialkyl ether of saidpolyethylene glycol.
 7. A process as claimed in claim 1 carried out inthe presence of an inert organic solvent based on ethylene oxide orpropylene oxide and having a boiling point of more than 300* C. and amolecular weight of less than
 1000. 8. A process as claimed in claim 1wherein said basic compound is a hydroxide, oxide, amide, acetate,propionate, carbonate, bicarbonate, alcoholate, alkylene glycolate ormonoether thereof with a sodium, potassium, calcium, barium or magnesiumcation.